Motion sensitive interlock for a vehicle having a breath analyzer

ABSTRACT

Apparatus for use with a vehicle is disclosed and comprises an interlock device. The device is adapted to, in use: at least while said vehicle is in motion, periodically generate a prompt; assess motion of said vehicle; at least when said vehicle is assessed by said device to be at rest, carry out an analysis operation wherein a breath sample is received and analyzed; and in the event that, within a predetermined period following a prompt, the device does not, while said vehicle is assessed to be at rest, carry out said analysis operation, enter an alarm state at least when the vehicle is in motion. The device can be adapted to carry out analysis operations only when the vehicle is assessed to be at rest.

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to, and claims the benefit of priority from,U.S. Provisional Application Ser. No. 61/303,336, filed Feb. 11, 2010,the disclosure of which is incorporated herein by reference in itsentirety.

FIELD OF THE INVENTION

The present invention relates to the field of automotive interlocks.

BACKGROUND OF THE INVENTION

It is well-known to secure a motor vehicle against operation by a personwho has consumed alcohol by installing in said vehicle a breath alcoholtester. A typical arrangement, known as an ignition interlock device(IID), involves a relay between the breath tester and the starter motor,pursuant to which the starter motor cannot be engaged until asatisfactory breath sample has been given. In this regard, a‘satisfactory’ gas sample is conventionally understood to be one that(i) is of sufficient volume and pressure to permit alcohol analysis;(ii) has alcohol concentration below a predetermined limit; and (iii)appears to have originated from the exhaled breath of a human being.Criteria (iii) is often assessed through measurements of pressure,humidity and temperature, but various other techniques such as humrecognition sensors are occasionally used. In some jurisdictions, aperson convicted of driving under the influence of alcohol may berequired by law to have a device of this type installed as a conditionassociated with the extension of driving privileges. While the engine isrunning, the IID will randomly require the driver to provide anotherbreath sample. The time between required breath samples is dependent onthe setting of the unit but it is typical for random breath samples tobe required every 10 to 20 minutes while the vehicle is in operation.The purpose behind the random breath sample is to prevent a driver fromhaving a “sober” friend blow into the device to start the vehicle and todeter drinking while driving. If the requested breath sample is notprovided or exceeds the predetermined limit, the device will record theincident, warn the driver and then start up an alarm (e.g., lightsflashing, horn honking, etc.) until the ignition is turned off or asatisfactory breath sample has been provided.

SUMMARY OF THE INVENTION

Apparatus for use with a motor vehicle forms one aspect of the presentinvention. This apparatus comprises: an interlock device, the interlockdevice being adapted to, in use: at least while said vehicle is inmotion, periodically generate a prompt; assess motion of said vehicle;at least when said vehicle is assessed by said device to be at rest,carry out an analysis operation wherein a breath sample is received andanalyzed; and in the event that, within a predetermined period followinga prompt, the device does not, while said vehicle is assessed to be atrest, carry out said analysis operation, enter an alarm state in whichone or more of the following are actuated at least when the vehicle isin motion: lighting forming part of the vehicle; auxiliary lightingcarried by the vehicle; the horn of the vehicle; auxiliary horn carriedby the vehicle; an event recording circuit; and an immobilizer circuit.

According to another aspect of the invention, the device can be adaptedto carry out analysis operations only when the vehicle is assessed to beat rest.

According to another aspect of the invention, when in use with a vehiclehaving an internal combustion engine, the device can be adapted to blockthe engine against starting except within: a predetermined periodfollowing an analysis operation which has resulted in a finding ofbreath alcohol concentration below a predetermined limit; and apredetermined period following an engine stall.

According to another aspect of the invention, wherein, following ananalysis operation, which has resulted in a finding of breath alcoholconcentration at or above the predetermined limit, the alarm state canbe entered.

According to another aspect of the invention, when in use with anelectric vehicle that is user-selectable between an operable state inwhich the vehicle is capable of being put into motor-driven motion andan inoperable state in which the vehicle is incapable of being put intomotor-driven motion, the device can be adapted, on entry into theoperable state from the inoperable state, to block motor-driven motionof the vehicle otherwise than in a predetermined period following ananalysis operation which has resulted in a finding of breath alcoholconcentration below a predetermined limit.

According to another aspect of the invention, wherein, following ananalysis operation, which has resulted in a finding of breath alcoholconcentration at or above the predetermined limit, the alarm state canbe entered.

According to another aspect of the invention, the analysis operation canresult in a finding of breath alcohol below the predetermined limit onlywhen the gas sample is determined by the device to originate from humanbreath.

According to another aspect of the invention, the determination of humanbreath origin can be based on one or more of: a hum sensor; ameasurement of humidity; a measurement of pressure; a measurement oftemperature; and a measurement of volume.

According to another aspect of the invention, the interlock device canassess motion of said vehicle in use via one or more of: the on-boarddiagnostic system of the vehicle; a speedometer of the vehicle; a GPSdevice; an internal accelerometer; an inertia sensor; cellulartelephonic signal triangulation; an odometer of the vehicle; the vehiclespeed sensor; an earth gravitational sensor; and a park sensor of thevehicle.

According to another aspect of the invention, the event recordingcircuit can be actuated in the event of receipt of a gas sample which isdetermined to have an alcohol concentration at or above a predeterminedlimit.

According to another aspect of the invention, the immobilizer circuit,when activated, can cause: the maximum attainable motor-driven velocityof the vehicle to decrease over time; and/or the maximum attainablemotor-driven velocity of the vehicle to decrease to nil if the vehicleis assessed to have been at rest for more than a predetermined period oftime.

According to another aspect of the invention, the rate of decrease ofthe maximum attainable motor-driven velocity of the vehicle can be afunction of vehicle location and/or vehicle speed.

According to another aspect of the invention, the immobilizer circuitcan be activated in the event that, within a predetermined period oftime following the prompt, the gas sampler does not receive and analyzea gas sample, the predetermined period of time being a function ofvehicle location and/or speed.

According to another aspect of the invention, the event recordingcircuit can (i) record the date and time at which the alarm state wasentered; and/or (ii) send, by wireless means, a message outlining thedate and time at which the alarm state was entered.

According to another aspect of the invention, when in use with a vehiclehaving a combustion engine, said periodic prompt generation can occurduring times when the engine is running.

According to another aspect of the invention, when in use with anelectric vehicle that is user-selectable between an operable state inwhich the vehicle is capable of being put into motion and an inoperablestate in which the vehicle is incapable of being put into motion, saidperiodic prompt generation can occur during times when the vehicle is inthe operable state.

According to another aspect of the invention, the immobilizer circuitcan be activated when the vehicle is in the alarm state.

According to another aspect of the invention, the periodic generation ofthe prompt may be suppressed while the vehicle is assessed to be atrest.

Other advantages, features and characteristics of the method, willbecome more apparent upon consideration of the following detaileddescription and the appended claims.

FIG. 1 is a view of an interlock according to an exemplary embodiment ofthe invention in use with a vehicle; and

FIG. 2 is a schematic view of the interlock of FIG. 1 in combinationwith germane systems of the vehicle.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT

An interlock device 20 according to an exemplary embodiment of thepresent invention is hereinafter described with reference to FIG. 1 andFIG. 2 but, as an initial matter, it will be understood that theexemplary interlock device 20 is for use with a motor vehicle 22.

This motor vehicle 22 is of a conventional type which is user-selectablebetween an operable state in which the vehicle is capable of being putinto motion by its motor and an inoperable state in which the vehicle isincapable of being put into motion by its motor. The user-selection isaccommodated by way of a mechanical key 24 that the user inserts in atumbler 26 arrangement; a partial turn activates the ignition circuit 27and a full turn activates the starter motor 28 of the vehicle, throughactuation of a starter solenoid 30. The nil-turn position corresponds tothe inoperable state; both partial and full-turn positions correspond tothe operable state. The vehicle 22 is also of the type including anOBD-II compliant On-Board Diagnostics System 32 that generates signalsincluding vehicle speed and vehicular operational state and is also ofthe type having an immobilizer circuit 34 for interfering with motion ofthe vehicle, for example, a switch in the circuit powering the fuel pump39.

Turning now to the exemplary interlock device 20, same should beunderstood to comprise a gas sampler 36, a siren 38, a controller 40, atone generator 43, a prompt light 45, a warning light 46 and a faillight 51.

The gas sampler 36 is of the fuel cell sensor type adapted to receiveand analyze a gas sample and produce a signal that varies in apredictable manner with alcohol concentration in the gas sample. Thesampler 36 is also of the type adapted to test the gas sample forpressure, temperature, flow, humidity and volume. On completion of ananalysis, the gas sampler 36 produces signals which are indicative ofthe analyses. The siren 38 is mounted in use in the engine compartment.

The controller 40 includes a computing device 42, a relay 44 and a GPSdevice 47.

The relay 44, in use, is interposed in the circuit powering the startersolenoid 30.

The computing device 42: is for receiving the signals produced by andactuating the gas sampler 36; is coupled to the relay 44, for actuationthereof; in use, is coupled to and receives signals from OBD-II circuit;in use, is coupled to the immobilizer circuit 34; is coupled to the GPSdevice 47; and has the following functions:

prompt generation enablement gas sampler actuation alarm analysis resetPrompt Generation

While the vehicle is in an operable state [i.e. in the describedembodiment, this being when the ignition switch is either in thepartially-turned or fully-turned position] the computing device 42periodically generates a prompt, which is audibly and visually signaledto the operator of the vehicle through actuation of the tone generator43 and prompt light 45.

The period between prompts is a random period that depends on the numberof prompts that have occurred since the vehicle last entered an operablestate; the random period preceding each prompt is relatively short incomparison to the random period between that prompt and the next prompt.

The random period is obtained through a random number generator and atimer which form part of the computing device 42. The tone generator 43and prompt light 45 are adapted to vary in intensity as a function ofthe location of the vehicle [as determined by the GPS] and the timeelapsed and distance driven since the issuance of the prompt. Forexample, in a heavily populated area, where a driver can spend arelatively long time travelling a relatively short distance whileencountering a relatively large number of pedestrians and other drivers,the intensity increases relatively rapidly and substantially in directrelation to elapsed time. In a lightly populated area, such as a loggingtrail, where a driver can, in a relatively short period of time, travelonly a relatively short distance and encounter relatively fewpedestrians and other drivers, the intensity increases relatively slowlyand is biased towards distance traveled. Where the information madeavailable by the GPS device suggests the vehicle is travelling on ahighway lacking shoulders, the intensity increases relatively slowlyuntil the vehicle approaches an exit, whereupon the intensity increasesrelatively quickly. Where the information made available by the GPSdevice suggests the vehicle is at rest and has been at rest for sometime, such as would be the case with a commercial vehicle at a reststop, the intensity is maintained at a low level until the vehicle isput into motion. The tone generator 43 and prompt light 45 aredeactivated on receipt of a gas sample, as discussed below.

Gas Sampler Actuation

When a prompt is issued, the computing device 42 assesses motion of thevehicle and, when the vehicle is determined to be at rest, based onreadings from the OBD-II circuit, actuates the gas sampler 36 forreceiving and analyzing any gas sample introduced thereinto [andproducing signals indicative of the analyses as aforesaid]. The gassampler 36 can also be actuated manually, when the vehicle is at rest.

Analysis

The computing device 42 receives the signals from the gas sampler 36 anddetermines:

-   -   if the readings from the gas sampler 36 are indicative of an        alcohol concentration at or in excess of a predetermined        threshold; and    -   if the readings of temperature, humidity, volume and pressure        (or hum) are indicative of the gas sample being of human origin,        i.e. if the gas sample should be viewed to be a breath sample

The predetermined threshold is a matter of choice for the jurisdictionof interest, and varies with the permitted BAC in that jurisdiction andassumed partition ratios. In the United States, for example, thepredetermined threshold would be set at 0.08 grams of alcohol perdeciliter of blood.

In the event of a reading at or in excess of a predetermined threshold,the gas sampler disables itself for a predetermined period of time andthe controller makes a suitable log entry.

Persons of ordinary skill are readily capable of manufacturing gassamplers of this type, and as such, details are neither required norprovided herein.

Alarm

The computing device 42 monitors the signals sent by the gas sampler 36and, in the event that, within a predetermined period following theprompt, the gas sampler 36 does not receive and analyze a gas sample, analarm state of the vehicle is triggered. At all times when the vehicleis in the operable configuration in the alarm state, the fail light 51and tone generator 43 are activated. At all times when the vehicle is inmotion in the alarm state, the siren 38 is actuated. The alarm state isalso triggered after a gas sample has been provided which, on analysis,reveals alcohol concentration at or above the predetermined threshold.The alarm state is deactivated on receipt of a gas sample or if thevehicle is switched into the inoperable state.

Enablement

The computing device 42:

-   -   i) otherwise than within a predetermined period following an        engine stall, as determined by OBD monitoring, disables the        vehicle automatically upon entry into the operable state        associated with the partial-turn position of the key;    -   ii) disables the vehicle automatically on receipt of a gas        sample by the gas sampler 36, as determined through monitoring        of the signals produced by the gas sampler 36;    -   iii) enables the vehicle on receipt of a gas sample which, on        analysis, is viewed to be a breath sample and which reveals        alcohol concentration below the predetermined threshold; and    -   iv) disables the vehicle automatically on entry into the alarm        state.

Disablement (i) occurs through appropriate actuation of the relay 44 inthe starter circuit, i.e. when the key 24 is inserted and partiallyturned, the starter relay 44 is disabled.

Disablement (ii) occurs through the arming of a lock-out subroutine,specifically, the subroutine sends a signal to the immobilizer circuit34. To clarify, on receipt of a gas sample by the gas sampler 36, asignal is sent to the immobilizer circuit 34 to incrementally reduceflow to the fuel pump. This state is signaled to the operator of thevehicle by illumination of warning light 46. The rate of reduction is afunction of vehicle location and vehicle speed. For example, in aheavily populated area, where a driver can spend a relatively long timegoing a relatively short distance while encountering a relatively largenumber of pedestrians and other drivers, a reduction to nil occurssubstantially immediately. In contrast, in a lightly populated area, thereduction occurs relatively slowly and to an amount which enables thevehicle to travel only at very low speeds.

Enablement (iii), i.e. following the delivery of a satisfactory breathsample to the device, involves an enablement of the starter relay 44, adisarming of the lock out subroutine by controller 42, a darkening ofany illuminated prompt 45, warning 46 and fail 51 lights, and asilencing of the tone generator 43 and siren 38.

Disablement (iv) occurs through the arming of a lock-out subroutine,specifically, the subroutine sends a signal to the immobilizer circuit34. To clarify, in the alarm state, a signal is sent to the immobilizercircuit 34 to incrementally reduce flow to the fuel pump. This state issignaled to the operator of the vehicle by illumination of fail light51. The rate of reduction is a function of vehicle location and vehiclespeed. For example, in a heavily populated area, where a driver canspend a relatively long time going a relatively short distance whileencountering a relatively large number of pedestrians and other drivers,a reduction to nil occurs relatively quickly. In contrast, in a lightlypopulated area, the reduction occurs relatively slowly and to a deminimis amount which enables the vehicle to travel at very low speeds.

Reset

When the vehicle is turned to the inoperable state, any active alarmstate is vacated.

Safety

The foregoing provides an interlock arrangement that has public safetyadvantages:

-   -   in order to start the vehicle, except in a predetermined period        following an engine stall, a satisfactory breath sample must be        provided; this minimizes the likelihood of an intoxicated person        gaining access to the road;    -   once the vehicle has been started, the operator is periodically        prompted to provide a breath sample. The device does not enable        the sample to be given until the vehicle has been brought to        rest, avoiding the attendant risk associated with the delivery        of a sample while in motion. The visual and audio prompt        increases in intensity over time, to encourage the driver to        provide a sample. In the event that the requisite sample is not        provided promptly [which might occur if the driver was drinking        while driving and was reluctant to give a sample] an alarm state        is entered. When the vehicle is in motion in the alarm state, a        siren is activated to draw outside attention to the vehicle,        improving public safety and heightening the likelihood of        intervention by law enforcement personnel. As well, in the alarm        state, the vehicle is disabled: in heavily populated areas, full        disability occurs relatively quickly; in lightly populated        areas, disability occurs more slowly and is only partial,        allowing the vehicle to be put into low-speed motion unless the        vehicle is brought to rest for a predetermined period of time,        in which event it is fully disabled;    -   at the roadside, once a sample has been given, the vehicle is        disabled, unless the breath sample is satisfactory in terms of        alcohol concentration. The level of disability varies with the        location of the vehicle. In heavily populated areas, where the        operator can be expected to be able to find assistance if        required, the vehicle is substantially fully disabled and        incapable of motion. In remote areas, where the operator might        suffer injury, the vehicle can be driven at low speed, unless        the vehicle is brought to rest for a predetermined period of        time, in which event it is fully disabled.

Whereas but a single exemplary embodiment is described, numerousvariations are possible.

For example, whereas in the exemplary embodiment, the device is for usewith a vehicle having a mechanical key actuator, other actuationdevices, such as RFID fobs and digital keypads, are contemplated.

As well, whereas in the exemplary embodiment, a siren is provided, whichis triggered on motion of the vehicle in the alarm state, it is possiblefor the alarm state to trigger one or more of: the siren; lights carriedby the vehicle; and the horn of the vehicle, with suitable modificationsto the control circuits.

Further, whereas in the exemplary embodiment, the alarm state activatesan immobilizer circuit, it is possible for the alarm state to interferewith motion of the vehicle by interaction with other systems, such asthe brake sensor or OBD-II port.

Further, whereas in the exemplary embodiment, the interlock deviceassesses motion of the vehicle through the OBD-II port, the device couldalternatively assess vehicle motion through other mechanisms, includingbut not limited to:

-   -   a speedometer of said vehicle;    -   the GPS device;    -   an internal accelerometer;    -   an inertia sensor;    -   cellular telephonic signal triangulation; and    -   a park sensor of said vehicle.

Additionally, whereas a fuel cell sensor is described, other sensorssuch as but not limited to infrared sensors, could be utilized.

As well, whereas in the exemplary embodiment indicated, the sensor is ananalog sensor capable of providing an indication of alcoholconcentration in air, the sensor could be of a binary type, and capableonly of determining if the predetermined threshold had been exceeded. Inthis regard, in many jurisdictions, the predetermined threshold is thatwhich is indicative of the presence of BAC in excess of 0.08 gramsalcohol per deciliter of blood.

Moreover, though the disclosure heretofore has largely focused oncontexts in which alcohol consumption is of interest, it should beunderstood that the embodiments of the present invention are applicableto other types of controlled substances as well, such as, for example, anarcotic drug (e.g., cocaine, heroin or marijuana). In such cases,appropriate detection equipment would be interfaced with an interlock ina vehicle or other machinery and could preferably operate insubstantially similar manner as the inventive equipment describedheretofore in connection with alcohol.

Additionally, whereas various specific types of interlock arrangementsare described herein, modifications are possible. For example, whereasthe exemplary embodiment utilizes a relay in the starter solenoidcircuit for disablement at start-up, the relay could be disposed in theignition circuit itself, or in any other circuit that must be triggeredin order to trigger the ignition circuit. Alternatively, the immobilizercircuit could be used for disablement at start-up. As well, whereas theimmobilizer circuit described is interposed in the fuel pump circuit,this is not necessary.

As well, whereas a specific motor vehicle is described, it will beemphasized that this vehicle forms no part of the invention. The presentinvention can be used with motor vehicles that do not have startermotors, for example, electric vehicles, and with vehicles that do nothave ‘ignition circuits’, for example, diesel vehicles. In the case of avehicle lacking a starter, for example, an electric vehicle, disablement(i) occurs through the issuance of suitable signals to the motorcontroller. In addition to automobiles, the invention can be used with,for example, buses, transport trucks, motorcycles and trains.

Further, whereas an ‘aftermarket’ device is arguably implied in thisdocument, it should be understood that in this description and in theaccompanying claims, the vehicle with which the interlock is used andthe interlock device could be defined by a vehicle having an OEMinterlock installed, with the interlock device and the balance of thevehicle being inoperable and incomplete except with one another.

As well, whereas in the exemplary embodiment, the gas sampler is adaptedmerely to assess through crude measurements of temperature, etc. whetherthe sample has been provided by a person, rather than, for example, amachine or a balloon, additional functionality could and would likely beadded, for greater utility. Conventional “hum” sensors could, forexample, be employed, to further ensure that the gas sample was of humanorigin; devices for recording attempts by the user to start the vehiclewhile intoxicated could be added, as is desirable in some jurisdictions;and various recorders and identification methodologies could beemployed, to assist in the identification of the person providing thesample.

Further, whereas in the exemplary embodiment described, variousenablement and disablement states are specified, it will be understoodthat these are functional concepts, only. Thus, whereas it is describedthat the vehicle is disabled automatically on receipt of a gas sample bythe gas sampler 36, it will be understood that this could be a positivedisablement, i.e. sending a trigger to disable the vehicle on receipt ofa gas sample or a negative disablement, i.e. sending a trigger whichmaintains a previously-created disabled state of the vehicle.

Further, whereas the exemplary embodiment contemplates that prompts willoccur at all times when the vehicle is running (or, in the case of anelectric vehicle, when the vehicle is in the operable state), theperiodic generation of the prompt may be suppressed while the vehicle isassessed to be at rest.

In view of these and other changes, it should be understood that theinvention is to be limited only by the accompanying claims, purposivelyconstrued.

The invention claimed is:
 1. Apparatus for use with a motor vehicle, theapparatus comprising: an interlock device, the interlock device beingadapted to, in use: at least while said vehicle is in motion,periodically generate a prompt; assess motion of said vehicle; only whensaid vehicle is assessed by said device to be at rest, carry out ananalysis operation wherein a breath sample is received and analyzed; andin the event that, within a predetermined period following a prompt, thedevice does not, while said vehicle is assessed to be at rest, carry outsaid analysis operation, enter an alarm state in which one or more ofthe following are actuated at least when the vehicle is in motion:lighting forming part of the vehicle; auxiliary lighting carried by thevehicle; the horn of the vehicle; auxiliary horn carried by the vehicle;an event recording circuit; and an immobilizer circuit wherein one ormore of the following conditions applies: the maximum attainablemotor-driven velocity of the vehicle decreases as a function of vehiclelocation and/or speed, when the immobilizer circuit has been activated;the predetermined period is a function of vehicle location and/or speed;the intensity of an audio signal associated with the prompt varies as afunction of vehicle location and/or speed; and the intensity of a visualsignal associated with the prompt varies as a function of vehiclelocation and/or speed.
 2. Apparatus according to claim 1, wherein, whenin use with a vehicle having an internal combustion engine, the deviceis adapted to block the engine against starting except within: apredetermined period following an analysis operation which has resultedin a finding of breath alcohol concentration below a predeterminedlimit; and a predetermined period following an engine stall. 3.Apparatus according to claim 2, wherein, following an analysis operationwhich has resulted in a finding of breath alcohol concentration at orabove the predetermined limit, the alarm state is entered.
 4. Apparatusaccording to claim 1, wherein, when in use with an electric vehicle thatis user-selectable between an operable state in which the vehicle iscapable of being put into motor-driven motion and an inoperable state inwhich the vehicle is incapable of being put into motor-driven motion,the device is adapted, on entry into the operable state from theinoperable state, to block motor-driven motion of the vehicle otherwisethan in a predetermined period following an analysis operation which hasresulted in a finding of breath alcohol concentration below apredetermined limit.
 5. Apparatus according to claim 4, wherein,following an analysis operation which is has resulted in a finding ofbreath alcohol concentration at or above the predetermined limit, thealarm state is entered.
 6. Apparatus according to claim 5, wherein theanalysis operation can result in a finding of breath alcohol below thepredetermined limit only when the gas sample is determined by the deviceto originate from human breath.
 7. Apparatus according to claim 6,wherein the determination of human breath origin is based on one or moreof: a hum sensor; a measurement of humidity; a measurement of pressure;a measurement of temperature; and a measurement of volume.
 8. Apparatusaccording to claim 1, wherein the interlock device assesses motion ofsaid vehicle in use via one or more of: the on-board diagnostic systemof the vehicle; a speedometer of the vehicle; a GPS device; an internalaccelerometer; an inertia sensor; cellular telephonic signaltriangulation; an odometer of the vehicle; the vehicle speed sensor; anearth gravitational sensor; and a park sensor of the vehicle. 9.Apparatus according to claim 8, wherein the event recording circuit isactuated in the event of receipt of a gas sample which is determined tohave an alcohol concentration at or above a predetermined limit. 10.Apparatus according to claim 1, wherein the immobilizer circuit, whenactivated, causes: the maximum attainable motor-driven velocity of thevehicle to decrease over time; and/or the maximum attainablemotor-driven velocity of the vehicle to decrease to nil if the vehicleis assessed to have been at rest for more than a predetermined time. 11.Apparatus according to claim 10, wherein the rate of decrease of themaximum attainable motor-driven velocity of the vehicle is a function ofvehicle location and/or vehicle speed.
 12. Apparatus according to claim11, wherein the immobilizer circuit is activated in the event that,within a predetermined period following the prompt, the gas sampler doesnot receive and analyze a gas sample, the predetermined period being afunction of vehicle location and/or speed.
 13. Apparatus according toclaim 9, wherein the event recording circuit (i) records the date andtime at which the alarm state was triggered; and/or (ii) sends, bywireless means, a message outlining the date and time at which the alarmstate was triggered.
 14. Apparatus according to claim 8, wherein, whenin use with a vehicle having a combustion engine, said periodic promptgeneration occurs during times when the engine is running.
 15. Apparatusaccording to claim 4, wherein, when in use with an electric vehicle thatis user-selectable between an operable state in which the vehicle iscapable of being put into motion and an inoperable state in which thevehicle is incapable of being put into motion, said periodic promptgeneration occurs during times when the vehicle is in the operablestate.
 16. Apparatus according to claim 3, wherein the immobilizercircuit is activated when the vehicle is in the alarm state. 17.Apparatus according to claim 1, wherein the periodic generation of theprompt may be suppressed while the vehicle is assessed to be at rest.